Abstract: C14.00011 : Abrupt Change of the Superconducting Gap Structure at the Nematic Quantum Critical Point in FeSe1-xSx*

4:54 PM–5:06 PM

Abstract

Presenter:

Yuki Sato(Department of Physics, Kyoto University)

Authors:

Yuki Sato(Department of Physics, Kyoto University)

Shigeru Kasahara(Department of Physics, Kyoto University)

Tomoya Taniguchi(Department of Physics, Kyoto University)

Xiangzhuo Xing(Department of Physics, Kyoto University)

Yuichi Kasahara(Department of Physics, Kyoto University)

Yoshifumi Tokiwa(Institute of Physics, Augsburg University)

Youichi Yamakawa(Department of Physics, Nagoya University)

Hiroshi Kontani(Department of Physics, Nagoya University)

Takasada Shibauchi(Department of Advanced Materials Science, University of Tokyo)

Yuji Matsuda(Department of Physics, Kyoto University)

FeSe offers an ideal platform to investigate the role of nematicity on the electron pairing interaction in iron-based superconductors. To reveal how the superconducting gap evolves with nematicity, we measure the thermal conductivity and specfic heat of FeSe1−xSx, in which the nematicity is suppressed by isoelectronic sulfur substitution and a nematic quantum critical point (NQCP) appears at xc ≈ 0.17. In the whole nematic regime, we find two-gap behavior; one is small but highly anisotropic with deep minima or line nodes, and the other is larger and more isotropic. In stark contrast, in the tetragonal regime, the larger gap becomes strongly anisotropic, demonstrating an abrupt change of the superconducting gap structure at the NQCP. As charge fluctuations of dxz and dyz orbitals are fundamentally different on the each side of NQCP, our observation directly implies that the orbital dependent nature of the nematic fluctuations has a strong impact on the superconducting gap structure and hence on the pairing interaction.

*This work was supported by Grants-in-Aid for Scientific Reserch (No. 25220710, 15H02106, 15H03688) and on Innovative Areas "Topological Materials Science" (No. 15H05852) from Japan society for the Promotion of Science (JSPS).